What is Williams syndrome?

Williams syndrome is a genetic condition characterized by unique facial features, delayed development, learning problems, and certain personality traits. People with Williams syndrome tend to have cardiovascular disease, connective tissue changes, and endocrine abnormalities. Growth abnormalities are also common: Williams syndrome may cause poor growth in childhood, and most adults with the condition are shorter than average.

Williams syndrome occurs in about one per 7,500 births. It may also be known as Williams-Beuren syndrome.

What causes Williams syndrome?

Williams syndrome is caused by a deletion, or missing piece, of a region on chromosome 7. Some important points to know about this genetic condition:

  • We have 46 chromosomes total arranged in to 23 pairs of 2. We inherit one copy of each chromosome in each pair from our mother, and the other copy in each pair comes from our father.
  • Within our chromosomes are segments of DNA (genetic information) known as genes. Our genes are like instructions that tell our body how to form and function properly. We have over 20,000 genes in each cell of our bodies.
  • Individuals with Williams syndrome are missing a portion of chromosome 7 that typically includes several genes. These missing genes or “instructions” result in the findings known to be common among people with Williams syndrome.
  • Williams syndrome is usually caused by a random genetic mutation, or error, in chromosome 7. This means that most people with Williams syndrome have not inherited the condition from a parent. People with Williams syndrome have a 50% chance of passing the condition on to each of their offspring.

What are the symptoms of Williams syndrome?

Williams syndrome may cause a range of developmental issues and symptoms. The condition is typically diagnosed in infancy or early childhood. Not all people with Williams syndrome will have the same set of symptoms.

One of the more serious features of Williams syndrome is cardiovascular disease. Narrowing of various blood vessels is common, especially peripheral pulmonic stenosis and supravalvular aortic stenosis, which can lead to increased blood pressure, arrhythmia (irregular heartbeat) and ultimately cardiac failure. Cardiac involvement is often one of the first signs that a child may have Williams syndrome.

Other common features of Williams syndrome include:

  • Characteristic facial features, especially in childhood, such as: full cheeks, wide mouth, prominent lips, small jaw, large ears, short/upturned nose, epicanthal folds (vertical skin folds that cover the inner corners of the eyes
  • Feeding difficulties in infancy, often leading to poor growth
  • Shorter than average height
  • Low body tone (hypotonia) and hyperextensible joints, which may result in delayed developmental milestones such as sitting and walking
  • Unique personality traits: overly friendly (lack of “stranger danger”), attention problems, excessive empathy, specific phobias, anxiety
  • Sleep problems
  • Speech delay in early childhood, although speech later becomes a relative strength
  • Intellectual disability, usually in the “mild” range
  • Endocrine abnormalities: elevated calcium level (particularly in infancy), hypothyroidism, early puberty, diabetes in adulthood
  • Farsightedness and/or eyes which do not align
  • Chronic ear infections and/or hearing loss
  • Dental abnormalities, such as poor enamel and small or missing teeth
  • Scoliosis (abnormal curvature of the spine)
  • Unsteady gait and/or tremor in adulthood

Many of the symptoms of Williams syndrome occur in other diseases that are not Williams syndrome. If you are concerned about these symptoms in yourself or in your child, you should seek an evaluation by a medical geneticist.

Last reviewed by a Cleveland Clinic medical professional on 05/29/2019.


  • Morris CA. Williams Syndrome. 1999 Apr 9 [Updated 2013 Jun 13]. In: Pagon RA, Adam MP, Ardinger HH, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2017. Available from: www.ncbi.nlm.nih.gov Accessed 7/3/2017.
  • National Organization for Rare Disorders. Williams Syndrome Accessed 7/3/2017.
  • Williams Syndrome Association. What Is Williams Syndrome? Accessed 7/3/2017.
  • Genetic Home Reference. Williams syndrome Accessed 7/3/2017.

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